Abstract <p>This study employed a Fe₃O₄ and carbon black system to conduct controllable etching of diamond particles through a high-temperature carbothermal reduction reaction, investigating the influence mechanism of carbon black content on the etching effect. The experimental results indicate that during the high-temperature reaction process, a significant carbothermal reduction reaction occurs between Fe₃O₄ and carbon black. When the carbon black content was within an appropriate range, the reaction system exhibits a favorable synergistic etching effect, resulting in a uniform etching morphology on the diamond surface. However, with the continuous increase in carbon black content, the etching effect shows a noticeable declining trend. This study provides a promising controllable etching method for diamond surface modification.</p>